1. Field of the Invention
The present invention relates to novel compounds or salts thereof having strong antibacterial activities against gram-positive bacteria, gram-negative bacteria and drug resistant bacteria, and antibacterial agents comprising the same.
2. Description of Related Art
Various antibacterial agents and synthetic antibacterial agents have been used in the treatment of infectious diseases by those involved in health care. However, various drug resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE) and penicillin-resistant Streptococcus pneumoniae (PRSP) have been emerging in recent years. It is a critical issue for physicians to treat patients who are infected with such drug resistant bacteria. Moreover, the emergence of multiply resistant bacteria, which have gained resistance to multiple drugs, is of serious concern worldwide as they cause intractable infectious diseases.
The development of antibiotics which are effective against the above mentioned drug resistant bacteria has been long-awaited. For example, the International Publication No. WO99/07682 (Patent Document 1) discloses the quinolone type compounds which are effective against MRSA. Moreover, in International Publication No. WO2004/002490 (Patent Document 2) and International Publication No. WO2004/002992 (Patent Document 3), the compounds which do not work by any known mechanisms of action have been described.
[Patent Document 1] International Publication No. WO99/07682
[Patent Document 2] International Publication No. WO2004/002490
[Patent Document 3] International Publication No. WO2004/002992
It is desired to develop a long-awaited agent which has sufficient safety and strong antibacterial activities against gram-positive bacteria, gram-negative bacteria and drug resistant bacteria.